This is a program that determines many properties of the C compiler
and machine that it is run on, such as minimum and maximum [un]signed
char/int/long, many properties of float/ [long] double, and so on.

As an option, it will also produce the ANSI C float.h and limits.h files.

As a further option, it will even check that the compiler reads the
header files correctly.

It is a good test-case for compilers, since it exercises them with
many limiting values, such as the ability to handle the minimum and
maximum floating-point numbers.